Zeolite is used as a catalyst, a catalyst carrier, an adsorbent, and the like. Zeolite has a molecular sieve function, and a zeolite membrane obtained by forming zeolite into a membrane shape is used as a gas separation membrane or a pervaporation membrane.
Zeolite is classified into LTA, MFI, MOR, AFI, FER, FAU, or DDR depending on the crystal structure. Of these, DDR (Deca-Dodecasil 3R) type zeolite is a crystal having silica as the main component and has pores in the crystal structure. The pore is formed by a polyhedron containing an oxygen eight-membered ring and has a pore size of 4.4×3.6 angstrom.
The DDR-type zeolite has a relatively small pore size among zeolite. Therefore, it can be used as an adsorbent or separation sieve for separating only low molecular gas such as helium (H2), carbon dioxide (CO2), methane (CH4), and ethane (C2H6), ethylene (C2H4), propane (C3H8), and propylene (C3H6).
Each of the non patent documents 1 to 3 discloses a process for the production of DDR-type zeolite. In these production processes, 1-adamantanamine is used as a structure directing agent (hereinbelow referred to as “SDA”), and tetramethoxysilane, ethylenediamine, and water are used as raw materials to produce a DDR-type zeolite powder of all silica containing no aluminum by hydrothermal synthesis.
Patent Document 1 discloses a technique where the processes for the production of DDR-type zeolite described in the non patent documents 1 to 3 are simplified. In this technique, after a DDR-type zeolite powder as seed crystals is added to and dispersed in the raw material solution containing 1-adamantanamine which is dissolved in ethylenediamine (or after immersing a support where a DDR-type zeolite powder as seed crystals adheres), hydrothermal synthesis is performed.